Back door for an automobile



FIG. 1 is a front perspective view of a back door for an automobile showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a left-side view thereof. 

The ornamental design for a back door for an automobile, as shown and described. 